1. Field of the Invention
The present invention relates to a bearing structure, a motor, and a fan apparatus.
2. Description of the Related Art
In known bearing structures for use in fans, motors, or the like, a plurality of ribs extending in an axial direction are typically provided on an inner surface of a cavity portion of a sleeve support portion arranged to support a sleeve having a rotating shaft inserted therein. The ribs press the sleeve, which is press fitted within the sleeve support portion, radially inward to retain the sleeve.
Such bearing structures have some disadvantages. For example, when the pressing force applied by the ribs of the sleeve support portion onto the sleeve is too small, the positioning of the sleeve and the rotating shaft may become so insufficient that a problem, such as sway of the rotating shaft, may occur. On the other hand, when the pressing force applied by the ribs of the sleeve support portion onto the sleeve is too large, the sleeve may be excessively compressed by the pressing force from the ribs such that the sleeve may be deformed, resulting in a failure to support the rotating shaft stably. Moreover, in some cases, the optimum amount of the pressing force to be applied by the ribs onto the sleeve varies at different axial positions on the sleeve.
For instance, an axial center of gravity of a rotating body including the rotating shaft is sometimes located in that portion of the cavity portion of the sleeve support portion which is located toward an opening portion, in an axial direction of the sleeve. Therefore, more careful control of the amount of the pressing force applied by the ribs onto the sleeve is required for that portion of the cavity portion than for the other portions.